Green Roof Plants: a Resource and Planting Guide - Tapa dura

The idea of greening a roof is not a new one and, in fact, dates back thousands of years. Civilizations in Mesopotamia originated the concept (Dunnett and Kingsbury 2004), and Greeks, Romans, Persians, and other cultures had some form of roof gardens to green and cool their often brutally hot landscapes. The famed "hanging gardens of Babylon," for example, were actually planted on rooftops. At the other climatic extreme, sod roofs have long graced homes in Scandinavia, providing extra warmth and insulation in cold, wet climates. Nature itself is the inspiration for green roofs, depositing seeds that germinate in leaf, dirt, and rock piles on garden sheds, in gutters, and on seemingly inhospitable, often flat, stretches of roof.

Green roofs did not attain widespread use until more recent times, and then only in parts of northern Europe, where the scarcity of land for new buildings, combined with the development of new roofing materials like concrete, were driving forces behind their modern adaptation. When Switzerland, Germany, Austria, and other countries embarked on a post-World War II building campaign, they utilized green roofs for practical, environmental, and aesthetic purposes. As cities expanded to the edges of the countryside, green roofs represented an innovative way to preserve green space, reduce the impact of development, and help filter and purify the air. Planted roofs increased oxygen output, softened urban streetscapes, reduced impervious surfaces, and contained storm water runoff to vital tributaries and major bodies of water that supplied drinking water to millions of people.